Diabetes is one of the most prevalent chronic disorders worldwide with significant personal and financial costs for patients and their families, as well as for society. Different types of diabetes exist with distinct etiologies and pathogeneses. For example, diabetes mellitus is a disorder of carbohydrate metabolism, characterized by hyperglycemia and glycosuria and resulting from inadequate production or utilization of insulin.
Noninsulin-dependent diabetes mellitus (NIDDM), often referred to as Type II diabetes, is a form of diabetes that occurs predominantly in adults who produce adequate levels of insulin but who have a defect in insulin-mediated utilization and metabolism of glucose in peripheral tissues. Overt NIDDM is characterized by three major metabolic abnormalities: resistance to insulin-mediated glucose disposal, impairment of nutrient-stimulated insulin secretion, and overproduction of glucose by the liver. It has been shown that for some people with diabetes a genetic predisposition results from a mutation in the gene(s) coding for insulin and/or the insulin receptor and/or insulin-mediated signal transduction factor(s), thereby resulting in ineffective insulin and/or insulin-mediated effects thus impairing the utilization or metabolism of glucose.
For people with Type II diabetes, insulin secretion is often enhanced, presumably to compensate for insulin resistance. Eventually, however, the B-cells fail to maintain sufficient insulin secretion to compensate for the insulin resistance. Mechanisms responsible for the B-cell failure have not been identified, but may be related to the chronic demands placed on the B-cells by peripheral insulin resistance and/or to the effects of hyperglycemia. The B-cell failure could also occur as an independent, inherent defect in “pre-diabetic” individuals.
NIDDM often develops from certain at risk populations. One such population is individuals with polycystic ovary syndrome (PCOS). PCOS is the most common endocrine disorder in women of reproductive age. This syndrome is characterized by hyperandrogenism and disordered gonadotropin secretion producing oligo- or anovulation. Recent prevalence estimates suggest that 5–10% of women between 18–44 years of age (about 5 million women, according to the 1990 census) have the full-blown syndrome of hyperandrogenism, chronic anovulation, and polycystic ovaries. Despite more than 50 years since its original description, the etiology of the syndrome remains unclear. The biochemical profile, ovarian morphology, and clinical features are non-specific; hence, the diagnosis remains one of exclusion of disorders, such as androgen-secreting tumors, Cushing's Syndrome, and late-onset congenital adrenal hyperplasia. PCOS is associated with profound insulin resistance resulting in substantial hyperinsulinemia. As a result of their insulin resistance, PCOS women are at increased risk to develop NIDDM.
NIDDM also develops from the at risk population of individuals with gestational diabetes mellitus (GDM). Pregnancy normally is associated with progressive resistance to insulin-mediated glucose disposal. In fact, insulin sensitivity is lower during late pregnancy than in nearly all other physiological conditions. The insulin resistance is thought to be mediated in large part by the effects of circulating hormones such as placental lactogen, progesterone, and cortisol, all of which are elevated during pregnancy. In the face of the insulin resistance, pancreatic B-cell responsiveness to glucose normally increases nearly 3-fold by late pregnancy, a response that serves to minimize the effect of insulin resistance on circulating glucose levels. Thus, pregnancy provides a major “stress-test” of the capacity for B-cells to compensate for insulin resistance.
Other populations thought to be at risk for developing NIDDM include persons with Syndrome X; persons with concomitant hyperinsulinemia; persons with insulin resistance characterized by hyperinsulinemia and by failure to respond to exogenous insulin; and persons with abnormal insulin and/or evidence of glucose disorders associated with excess circulating glucocorticoids, growth hormone, catecholamines, glucagon, parathyroid hormone, and other insulin-resistant conditions.
Failure to treat NIDDM can result in mortality due to cardiovascular disease and in other diabetic complications including retinopathy, nephropathy, and peripheral neuropathy. There is a substantial need for a method of treating at risk populations such as those with PCOS and GDM in order to prevent or delay the onset of NIDDM thereby bringing relief of symptoms, improving the quality of life, preventing acute and long-term complications, reducing mortality and treating accompanying disorders of the populations at risk for NIDDM.
For many years, treatment of NIDDM has involved a program aimed at lowering blood sugar with a combination of diet and exercise. Alternatively, treatment of NIDDM can involve oral hypoglycemic agents, such as sulfonylureas alone or in combination with insulin injections. Recently, alpha-glucosidase inhibitors, such as a carboys, have been shown to be effective in reducing the postprandial rise in blood glucose (Lefevre, et al., Drugs 1992; 44:29–38). In Europe and Canada another treatment used primarily in obese diabetics is metformin, a biguanide.
Compounds useful in the treatment of the various disorders discussed above, and methods of making the compounds, are known and some of these are disclosed in U.S. Pat. No. 5,223,522 issued Jun. 29, 1993; U.S. Pat. No. 5,132,317 issued Jul. 12, 1992; U.S. Pat. No. 5,120,754 issued Jun. 9, 1992; U.S. Pat. No. 5,061,717 issued Oct. 29, 1991; U.S. Pat. No. 4,897,405 issued Jan. 30, 1990; U.S. Pat. No. 4,873,255 issued Oct. 10, 1989; U.S. Pat. No. 4,687,777 issued Aug. 18, 1987; U.S. Pat. No. 4,572,912 issued Feb. 25, 1986; U.S. Pat. No. 4,287,200 issued Sep. 1, 1981; U.S. Pat. No. 5,002,953, issued Mar. 26, 1991; U.S. Pat. Nos. 4,340,605; 4,438,141; 4,444,779; 4,461,902; 4,703,052; 4,725,610; 4,897,393; 4,918,091; 4,948,900; 5,194,443; 5,232,925; and 5,260,445; WO 91/07107; WO 92/02520; WO 94/01433; WO 89/08651; and JP Kokai 69383/92. The compounds disclosed in these issued patents and applications are useful as therapeutic agents for the treatment of diabetes, hyperglycemia, hypercholesterolemia, and hyperlipidemia. The teachings of these issued patents are incorporated herein by reference in their entireties.
Drug toxicity is an important consideration in the treatment of humans and animals. Toxic side effects resulting from the administration of drugs include a variety of conditions that range from low-grade fever to death. Drug therapy is justified only when the benefits of the treatment protocol outweigh the potential risks associated with the treatment. The factors balanced by the practitioner include the qualitative and quantitative impact of the drug to be used as well as the resulting outcome if the drug is not provided to the individual. Other factors considered include the physical condition of the patient, the disease stage and its history of progression, and any known adverse effects associated with a drug.
Drug elimination is typically the result of metabolic activity upon the drug and the subsequent excretion of the drug from the body. Metabolic activity can take place within the vascular supply and/or within cellular compartments or organs. The liver is a principal site of drug metabolism. The metabolic process can be categorized into synthetic and nonsynthetic reactions. In nonsynthetic reactions, the drug is chemically altered by oxidation, reduction, hydrolysis, or any combination of the aforementioned processes. These processes are collectively referred to as Phase I reactions.
In Phase II reactions, also known as synthetic reactions or conjugations, the parent drug, or intermediate metabolites thereof, are combined with endogenous substrates to yield an addition or conjugation product. Metabolites formed in synthetic reactions are, typically, more polar and biologically inactive. As a result, these metabolites are more easily excreted via the kidneys (in urine) or the liver (in bile). Synthetic reactions include glucuronidation, amino acid conjugation, acetylation, sulfoconjugation, and methylation.
One of the drugs used to treat Type II diabetes is troglitazone. The major side effects of troglitazone are nausea, peripheral edema, and abnormal liver function. Other reported adverse events include dyspnea, headache, thirst, gastrointestinal distress, insomnia, dizziness, incoordination, confusion, fatigue, pruritus, rash, alterations in blood cell counts, changes in serum lipids, acute renal insufficiency, and dryness of the mouth. Additional symptoms that have been reported, for which the relationship to troglitazone is unknown, include palpitations, sensations of hot and cold, swelling of body parts, skin eruption, stroke, and hyperglycemia. Accordingly, forms of glitazones which have fewer, or no, adverse effects (i.e., less toxicity) are desirable.
The principal difference between the compounds of the present invention and related compounds is the presence of a carboxyl group, either OOC— or COO—, directly attached to the 4-position of the phenyl ring. In the literature, thiazolidinediones having similar therapeutic properties have an ether function at the 4-position of the phenyl ring instead of a carboxyl group.
The presence of the carboxyl group has significant consequences for the biological behavior of these new compounds. The present compounds are primarily metabolized by hydrolytic enzymatic systems, whereas compounds having an ether function are metabolized only by oxidative enzymes. Hydrolytic enzymatic systems are ubiquitous, non-oxidative, not easily saturable, and non-inducible, and, therefore, reliable. By contrast, oxidative systems are mediated by the P-450 isozymes. These systems are localized, mainly, in the liver, saturable and inducible (even at low concentrations of therapeutic compounds) and therefore are highly unreliable.
The compounds of the subject invention do not rely on saturable hepatic systems for their metabolism and elimination, whereas the prior art compounds exert a heavy bio-burden on hepatic functions, especially in the presence of other drugs that rely on similar enzymes for detoxification. Thus, the present compounds have a much more desirable toxicity profile than prior art compounds, especially when considering liver toxicity and potentially fatal drug-drug interactions.
Upon metabolism by plasma and tissue esterases, the compounds of this invention are hydrolyzed into 2 types of molecules: 1) an alcohol or a phenol, and 2) a carboxylic acid. Therefore, any compound that yields compound 1, compound 2, compound 3, or compound 4, as defined in Table I, as a primary metabolite falls under the definition of this invention. This concept is illustrated in FIG. 1, taking compound 9 (of Table I) and compound 145 (of Table X) as specific examples of compounds giving 1 and 3, respectively, upon non-oxidative metabolism by esterases.